Drills and drill bits may have a variety of elements and functions including: piloting the drill, forming the hole, countersinking a recess, top and bottom countersinking a sheet, depth stopping, counterboring a plug, adjusting for depth, reaming, taper drilling for screws, one or more flutes for directing the cuttings, a barb for chip removing, providing a channel for coolant, a twist drill cut for channeling shavings, variable flight (flute axis), chamfering, and a multiplicity of concentric bores.
Drills and bits may have a variety of shapes including flat or spade type, a twist design with one or more helical channels, a semicylindrical axis, a conical or deburring shape, or a stepped conical design.
The desirable tool combines the functions needed in one tool, usable in one drilling operation, with a design maintaining sharpness, for lengths matching standard screw sizes.
Many United States patents have previously disclosed drills or drill bits with a wide variety of designs and functions:
U.S. Pat. No. 60,207 shows a flat, spade drill with a countersink bulge.
U.S. Pat. No. 252,704 discloses twist, spade, and conical drills with a countersink.
U.S. Pat. No. 1,471,866 shows a fluted twist drill with both top and bottom countersinking.
U.S. Pat. No. 1,711,012 discloses a conical drill with both stop and countersink elements.
U.S. Pat. No. 2,362,260 teaches a fluted twist drill with a countersink.
U.S. Pat. No. 2,389,909 shows a twist drill for reaming, counterboring, countersinking, and chamfering with a coolant.
U.S. Pat. No. 2,415,329 discloses a center drill for recesses and step-reams.
U.S. Pat. No. 2,655,964 teaches a flat drill with countersink stop and taper.
U.S. Pat. No. 2,732,869 shows a flat drill which can be twisted, a bore, a countersink, and a depth stop.
U.S. Pat. No. 2,886,081 discloses a flat blade which can be curled, pilots, cuts, countersinks, and has a depth stop.
U.S. Pat. 2,897,696 shows a three-webbed conical drill with cutting shoulders.
U.S. Pat. 2,981,127 discloses a variegated group of drills of the flat and twist types with chip-removing means.
U.S. Pat. No. 3,365,773 shows a deburring cone.
U.S. Pat. No. 3,564,945 teaches a multistep, conical drill with three flutes and noncutting shoulders.
U.S. Pat. No. 3,645,640 teaches a multistep, conical drill with a depth limit and an internal spring for controlling a blade.
U.S. Pat. No. 3,758,222 discloses a multistep, single-fluted, conical, tapered drill with helical connections for drilling holes in metal sheets.
U.S. Pat. No. 3,836,278 shows a slotted conical drill bit.
U.S. Pat. No. 4,127,355 teaches a multistepped, conical, single-fluted wood bit with helical connections.
U.S. Pat. No. 4,189,266 discloses an angularly multistepped drill bit with biased flutes.
U.S. Pat. No. 4,449,865 teaches a tool with a planar tip for drilling tapered, countersunk holes in composite materials.
U.S. Pat. No. 4,536,107 shows a twist drill with a threaded tip to reduce the size of chips.
U.S. Pat. No. 4,582,458 discloses a beveled, multistep, set of cylindrical surfaces having conical interfaces with zero pitch and biased double flutes.